1. Field of the Invention
This invention relates to a sanitary rubber article whose surface property is improved by coating a surface of a rubber molded article with a modified organopolysiloxane composition through bridge formation and a process for the production of the same. The sanitary rubber article of the present invention is useful as rubber parts of medical instruments or machines and as rubber articles for medicaments.
2. Description of the Prior Art
Various methods have hitherto been proposed for the purpose of improving the surface property of a molded rubber material, for example, decreasing the surface friction resistance, imparting a solvent resistance, water repellence or ozone resistance, removing the adhesiveness, etc. For example, there have been proposed a process comprising holding a rubber article in chlorine or bromine gas or in a solution of sodium sulfonate (Japanese Patent Publication No. 3807/1982), a process comprising holding in a fluorine gas atmosphere (Japanese Patent Publication No. 19464/1983 and Japanese Patent Laid-Open Publication No. 218830/1984), a process comprising coating a rubber surface with an organopolysiloxane composition such as containing an organopolysiloxane having two or more hydroxyl groups bonded to silicon atoms in one molecule, polydiorganosiloxane with both terminal hydroxyl groups blocked, polyorganohydrogensiloxane, epoxy group-containing siloxane and amino-or alkoxy group-containing siloxane, followed by hardening (Japanese Patent Publication No. 47864/1981), a process comprising preparing a medical or sanitary rubber article by incorporating 0.1 to 10% by weight of an organo silicon compound capable of moving little by little in the rubber (Japanese Patent Publication No. 30089/1972), a process comprising coating the surface of a rubber molded article with a silcone raw rubber containing hydroxyl or methoxy groups in the molecule through bridge formation thereof (Japanese Patent Laid-Open Publication No. 96837/1982) and a process comprising producing a rubber stopper by coating and bridging a polydimethylsiloxane or a polydimethylsiloxane in which a part of the dimethyl groups is replaced by phenyl groups, vinyl groups, fluorine-containing groups, polyether groups, alkylallyl groups or fatty acid groups (Japanese Patent Laid-Open Publication No. 182418/1982). The inventors have also proposed a process comprising coating a rubber surface with a silane coupling agent containing amino groups as disclosed in Japanese Patent Laid-Open Publication No. 104672/1981.
In the case of producing sanitary rubber articles by the prior art as described above, however, there arise problems that the adhesive or adsorptive property remains or a medicament or food is contaminated with the coated polysiloxane composition which will enter the human body, and accordingly, these rubber articles can hardly be considered to be excellent.
Coating of the surface of a sanitary rubber article with a polysiloxane with a small thickness is a good method, but on the other hand, this method has disadvantages, for example, unevenness in coating thickness, foreign matters due to peeling of the coating, occurrence of fine particles, insufficiency of friction resistance, etc., and meets with problems, for example, on fitting to an instrument or machine. Furthermore, of late, it has eagerly been desired to develop a sanitary rubber article, for example, sanitary rubber stopper which can easily be handled in automatic operations.